What do bees look like when they're dying?

Question

I have two bee hives in my back garden, and they are very very close together. Sometimes there are a couple of bees sitting on top of the hive and stay very still and jerk the back of their bodies closer into themselves almost like they're flexing muscles. Also, I noticed a seemingly grey bee do this once.

Do bees get old and grey? Sometimes big and healthy looking bees do this same thing, so I had a suspicion that perhaps if they were dying they may have stung something, and that was why the back of their bodies was pulsating.

Anyhow, please let me know.

p.s. I don't mean waggle dance

Answer 1

http://cache.daylife.com/imageserve/07pd...

Answer 2

bees fall to the floor when they are about to die.. so if you see one crawling on the floor its most likely dying.